Using Outlook for iOS for personal email and calendar management
Sorry to hear you're having trouble with this. Could you please confirm which three-dot menu you are using: the one directly next to/under the individual email date, or the three-dot menu for the full conversation?
In Outlook for iOS, the three dots for an individual message normally show options such as Reply, Reply All, Forward, and Delete. The Print option is available from the three-dot menu for the conversation instead. Please try opening the email conversation and tapping the three dots at the top-right of the conversation, then check whether Print appears there.